This invention relates to an improved drip chamber for use in an intravenous set.
Intravenous sets for the administration of parenteral solution to a patient typically include a piercer for insertion into a parenteral solution container, flexible tubing for transporting the parenteral solution from the container to the patient, a lower flow control clamp which acts on the flexible tubing to control the flow rate of the parenteral solution, and a needle adapter to which an intravenous needle is attached. The flow rate is determined by a flow meter such as a drip chamber positioned upstream of the lower clamp.
The intravenous set may also include a volume limiting chamber positioned between the piercer and the flow meter and an upper flow control clamp positioned upstream of the volume limiting chamber. The volume limiting chamber is used to precisely control the volume of parenteral solution administered to the patient. The volume limiting chamber is commonly designed to automatically shut off after a measured volume of parenteral solution is fed to the patient. This is accomplished in many intravenous sets by a membrane valve mounted in the bottom of the volume limiting chamber. Basically, the membrane valve comprises a material which when wet will pass parenteral solution but will not pass air at normal intravenous administration pressures.
A parenteral solution passage is provided in the volume limiting chamber for transferring parenteral solution from the chamber, typically directly into a flow meter. When a drip chamber is used as the flow meter, the discharge opening of the parenteral solution passage in the volume limiting chamber comprises a drop-forming orifice for forming drops of predetermined size. The drops emerge from the drop-forming orifice and fall through the drip chamber where they are counted per unit time and the flow rate of the parenteral solution thereby determined. Smaller size drops are preferred in certain applications, particularly for intravenous sets used in pediatric applications, and so the drop-forming orifice of the volume limiting chamber is frequently adapted to accept a plastic plug containing a very small diameter metal tube or cannula which will form small size drops, commonly sixty drops per cubic centimeter. In any event, it is obvious that the drip chamber will not function properly unless sufficient air space is provided below the drop-forming orifice for the rate of drop formation to be observed.
In using an intravenous set of this type, both the upper and lower control clamps are closed and the piercer is inserted into the outlet of a parenteral solution container. The upper flow control clamp is then opened and the volume limiting chamber partially filled with parenteral solution. After the upper flow control clamp is again closed, the set must be primed. This is accomplished by opening the lower flow control clamp, squeezing the drip chamber and then closing the lower flow control clamp. The drip chamber is then released and will partially fill with parenteral solution. This priming step is repeated until the drip chamber is approximately half filled. The lower flow control clamp must be opened during the priming operation so that the membrane valve will not be damaged. This priming operation is tedious and time consuming and runs the risk of damaging the delicate membrane valve unless strictly followed.
Furthermore, it sometimes happens that the nurse or other attendant will prime the drip chamber to such a high liquid level that insufficient air space remains for the drop rate to be determined. The liquid level can also become too high even when the drip chamber is properly primed. Parenteral solutions are commonly vacuum packed. As a result of this, the parenteral solution is capable of absorbing air from the air space in the drip chamber. This absorbtion of air causes a decrease in the volume of air in the drip chamber and a consequent increase in the volume of parenteral solution in the drip chamber which raises the liquid level. Since the membrane valve in the volume limiting chamber will not pass air when wet, there is no convenient way of admitting air into the drip chamber to lower the liquid level once the level has risen too high. Consequently, the expensive intravenous set is rendered useless because the flow rate therethrough cannot be determined.
Accordingly, an object of this invention is to provide an improved drip chamber.
A further object of this invention is to provide an improved drip chamber having an air vent.
Yet a further object of this invention is to provide an air vent in a drip chamber which includes an air filter.
Another object of this invention is to provide an improved drip chamber in which air can be vented to or from the drip chamber when it is desired to change the liquid level in the drip chamber.
Yet another object of this invention is to provide an improved intravenous set having a volume limiting chamber with a membrane valve and a drip chamber in which air can be vented to or from the drip chamber when it is necessary to adjust the liquid level in the drip chamber.
A still further object of this invention is to provide an improved drip chamber in which the liquid level can be lowered without damaging the delicate membrane valve in the volume limiting chamber.
Yet another object of this invention is to provide an air vent in a drip chamber to facilitate priming the drip chamber.